EvolvedGS3

I recently put a turbo in my 2000 GS300, and ended up having some drivability issues pre boost.

I have a basic turbo setup. Apexi Neo for fuel correction, Stock everything else.

My drivability issues came in the form of, misfire's, lean condition CEL's, Rich condition CEL's, and just poor drivability. At times I was unable to get over 2500 RPM's.
Once I was able to get into boost, the problem appeared to be gone. but the second it was back in vaccuum it sucked to drive again.
I changed my MAF location over from draw through, to blow through. Which I thought had solved the problem, but it appears that it was me resetting the ECU that actually had temp fixed the problem.
Resetting the ECU by disconnecting the battery was the only way to get rid of the problem for a short time. Until the ECU started making changes to the Long Term Fuel Correction map.




As I was reading around trying to figure this out, I noticed that some others were having similar problems with their car's. Most blamed the MAF.

Here is what was taking place on my GS300.
I had wired my primary O2 sensors together so Bank 1 and Bank 2 S1's were seeing the same voltage.
Both secondary 02's were installed. One went on the Down Pipe, the other (due to harness location) went onto the mid pipe.
Since I am not running any catalytic converters at this time (want to work out all the bugs before I put one on) I expected to get some check engine lights.

What the ECU saw was two different voltages from the secondary O2's. (whether this was caused by the different location, or some unknown variable is irrelivant)
Which it then interperted as a fuel correction issue.
Long term fuel correction bank 1 went as low as -28%
Long term fuel correction bank 2 went as high as 28%
AT THE SAME TIME.


The drivability issue that I was having was due to the factory ECU's correction of the fuel map.


Solution:
I ordered the universal o2 simulator dual output from o2simulator.com
After wiring it up (FYI, there is an ecu pinout that you can find online by goggeling it. BE CAUTIOUS, Jeff something or another's pinout is wrong on the location of one of the secondary O2 sensor wires. I have it written down incase anyone else needs the right pinout)
I have noticed that the car's long term fuel correction stay's roughly at 0. Short Term fuel correction plays around a little bit, but overall is pretty consistant to what it did in NA form.

Drivability is fixed, no issues, no need to reset the ECU every time I want to drive anywhere, no more disconnecting the primary O2's to keep it in Open Loop.
I am currently testing out whether the ECU will correct my tuning as the fuel map richen up when I am in boost.
As of yet, I have yet to see a check engine light for misfire, o2, or any other CEL.
around town drivability is perfect.

Thought this might help someone else out there.

-evolved

ROPADOPA

I always wondered what the NA ecu thought when it saw positive pressure (boost) vs negative (vacuum) as it was reading vacuum its whole life. LOL

You are just starting to figure out all the hang ups of NAT , good luck and either keep spending more money or face the facts that toyota builds perfectly good boosted motor with supporting electronics. GTE

schase

good stuff
ima def gona buy me the 02 sim

ElitistK

iTrader: (4)

not really; at the end of the road, a build na-t equals to a built gte. vvti ge has a MAF sensor so it does not read things in terms of pressure. however, his post is not entirely false; as long as you're on a piggyback you are always playing tricks on the stock ecu, and using other tricks to keep the tricks in play properly which leads to more and more tricks.

i would still prefer a gte setup though just for the packaging.

smuv gs3

iTrader: (1)

I'm glad you figured out some of your problems , I pm'ed you about my maf issues and I just gave up and sent the car back to the shop to let the tuner figure it out and install my haltech, sometimes I wonder if I should have done a swap instead.

ROPADOPA

Your right i keep forgetting that the Na air flow meter is a hot wire set up and not a Kartman and the ECU dosent read pressure or vacume. definatly right with the tricky part though

gs30062-1

Did you change the way you had the primary o2's wired when you installed o2 simulator?

JeffTsai

iTrader: (1)

I still need to fix the diagram for the 98-01GS lol. The 02+ is what I have is correct for sure because I used it on my car. How much power are you running? You will realize very quickly once you increase power the SAFC will be very very finicky. I recommend people to use a standalone for the most consistancy and power. But of course not everyone is willing to spend the money to do that.

If you're willing to read the below, this is some stuff I have learned in the EFI University courses I've taken.

The problem with running a piggyback is that the stock ecu has many many maps. Not just one, two, or three. It has somewhere in the range of 10-20+. It has many different maps for variables in temperature, loading, o2 feedback ranges, fuel octane, etc. So yeah, you tune the car perfectly to run on one map and it works pretty good. However, the next day you jump in the car, the stock ECU senses a different startup condition and goes to another map. Now your tuned settings will no longer be tune on this new map and can even risk blowing up the engine at elevated power levels. This is why many tuners put a relay to reset the ECU(by disconnection power) to it's first power on map. Thus the car will always run on that one map. If the car starts acting up all you have to do is key it off for a bit and restart it.

One other thing when you tune with a piggy. You are tricking the ecu to move into a different load cell on the map. Usually you will request a lower load cell if you are running bigger injectors to lower the duty cycle to get the correct AFR. The problem is that in lower load cells, the timing is much more aggressive. It's tuned that way to get maximum fuel efficiency and power when at a lower load, but is dangerous to run that advanced of timing when at higher load.

So basically what you're doing is tricking the ECU to request a lower load cell so you can target the correct AFR, however at the same time you're inadvertently bumping up the timing several degrees. I don't have to tell you that full boost + highly advanced timing = boom. The myth that people started "leaner is meaner". They thought by pulling out fuel they gained power, but in reality they were bumping up the timing and pulling out fuel at the same time!!!

All engines will produce the same poewr within broad AFR window. In most cases you will make the same power at 11:1 AFR and 13:1 AFR under boost. The ignition timing is what makes the power, however we usually tune on the richer side (around 11.5:1 under full boost on a 2JZ) for heat management. The fuel cools down the engine so it doesnt melt down. You will make the same amount of power at 11 or 13AFR, but one is safe and the other isn't.

If you use a piggyback at least use an AEM FIC or Greddy emanage ultimate, both those units can pull timing back to prevent detonation. However the best way to make the most power consistantly will be to....USE A STANDALONE

EvolvedGS3

Words of wisdom.
I mean that in the humble way. Not the sarcastic way.

Currently running 7psi on the car. I keep an eye on the LTFC, and run a wideband. I dont really push the car at all right now. Need to figure out what I am going to eventually do with it.

currently researching standalone ecu's.
liked your writeup on AEM's that you posted up on is.

Havent decided on going with the AEM yet. I had great results with a haltec a few years ago, might give them another shot again.

JeffTsai

iTrader: (1)

No problem, I'm always glad to help out others. If you need to ask anything else feel free to. I'm kinda busy at times, but I will get to your question sooner or later lol.

MDSC

iTrader: (3)

If you got a mild na-t set up i dont blame you for using cheap tunning software like SAFC...etc. But if you making over 500rwhp please spend some money on a stand alone and tune your car right before you blow it up.